1. Field of the Invention
The invention relates to a diagnostic apparatus and, more particularly to an apparatus for detecting breathing abnormalties in humans.
2. Prior Art
Breath sounds generated by humans are of two primary types, namely, tracheal (also referred to as bronchial) breath sounds which are generated by the passage of air through the major airways between the mouth and the lungs, and vesicular breath sounds which are normally detected over most of the chest of a human. These sounds have heretofore generally been observed by placing a stethoscope over the major airways in the case of broncheal sounds or other areas of the chest in the case of vesicular sounds and listening to the sounds directly. More recently, the observations have been assisted by the use of an electronic stethoscope which amplifies the breath sounds.
Abnormal breath sounds can frequently provide significant information about pulmonary and associated abnormalities which are not readily detected by other means such as roentgenographic examination. The major types of abnormal breath sounds have been described by various observers. A useful and commonly used classification divides abnormal (or adventitious, that is, unexpected) breath sounds into two major types, namely, pulmonary and pleural. The pulmonary sounds are divided into rales, which are discontinuous (interrupted) sounds, and rhonchi, which are continuous (uninterrupted) sounds. These are further subdivided into coarse, medium and fine rales, and sibilant and sonorous rhonchi. The pleural sounds are divided into friction rub sounds and various sounds of the left pneumothorax or pneumomediastinum.
Heretofore it has been difficult for an observer to detect the various breathing abnormalities, since they are frequently of short duration, sometimes of relatively low amplitude, and generally mixed in with normal breathing sounds which sometimes obscures the abnormal sounds. Further, some of these abnormalities are difficult to distinguish from each other. When the breath sounds are monitored aurally only, the differing characteristics and observational abilities of the observer tends to play a disproportionately large role in the diagnosis because of the difficulty in aurally indentifying and classifying the sounds, and thus the diagnostic conclusions drawns from these examinations are frequently highly variable. Recordings of these sounds at conventional strip-chart recordings speeds (25-50 mm/sec) provide little additional assistance in the analysis. These factors have greatly contributed to the lack of widespread utilization of abnormal breath sounds as a useful diagnostic tool
Attempts have been made to remedy this problem by mathematically analyzing the various breath sounds. This has been done by recording the sounds on a recording medium such as a magnetic tape, paper tape, or other permanent record medium and feeding the recorded data to a data processor for various analyses. For example, various studies have been directly toward analyzing the spectral frequency of the sounds, their relative amplitudes, correlation characteristics, etc. These highly sophisticated techniques have provided some generalized information about the various breath abnormalities, but have not heretofore yielded any practical, clearly defined, consistently repeatable method of distinguishing the various abnormalities or insuring their detection. Further, they are time consuming and expensive and require access to substantial equipment not commonly available outside research facilities; thus, they are not readily suited for widespread clinical use.